Throat plate for sewing machines



March l4, 1950 I I I zElER 2,500,731

' THROAT PLATE F OR SEWING MACHINES Filed Sept. 25, 1945 2 Sheets-Sheet 1 47% F I I 22 33' nws 6 12- L I j l March 14, 1950 1 F. F. zElER 2,

THROAT PLATE FOR SEWING MACHINES Filed. saga. 25, 1945 2 Sheets-Sheet 2 I I gwuwtfoc yreden'oz jade/2nw -44", i3 gt gg Patented Mar. 14, 1950 THROAT PLATE FOR SEWING MACHINES Frederick F. Zeier, Stratfield, Conn, assignor to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application September 25, 1945, Serial No. 618,484

2 Claims.

This invention relates to sewing machines and more particularly to sewing machine throatplates.

The invention has for its primary object the provision of an improved throat-plate which will effectively dissipate the force of the successive blows directed thereupon by a work-engaging element, to the end that the noise and vibration resulting from the blows are materially lessened.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

When a sewing machine is operated at speeds of 5000 R. P. M., a presser-foot opposed to a lower four-motion feed-dog has a tendency to remain slightly elevated above the throat-plate or, if it does engage the throat-plate, it will exert so little downward pressure that the effectiveness of the work feeding mechanism is substantially reduced. To overcome this objection, it has become the practice to increase the presser-bar spring pressures to the end that the presser-foot will be maintained under pressure in engagement with the work at all times, in spite of the high speed operation of the machine. However, by thus increasing the presser-bar spring pressure in a machine of the present type in Which a reciprocatory presser-foot and a top feed-foot are employed, it has been found that excessive noise and vibration have been set up. This noise and vibration result from the force of the Successive blows directed upon the throat-plate by the reciprocating presser-foot and the top feed-foot. This noise and vibration are particularly objectionable when the machine is operating in the low or medium speed ranges, as it is at this time that the full presser-bar spring pressure would not be required to prevent the presser-foot from lifting off the work.

The present improvement was devised in order to obviate the above noted difliculties. In the accompanying drawings, Fig. 1 represents a top plan view of a portion of a sewing machine bed-plate with a throat-plate secured thereto.

Fig. 2 represents a vertical section of the machine taken substantially along line 2-2 of Fig. 1 and it also discloses portions of a sewing machine feeding and stitching mechanisms.

Fig. 3 represents an enlarged vertical section of the bed-plate and throat-plate taken substantially along line 3-3 of Fig. 1.

Fig. 4 represents a vertical section of the bedplate and throat-plate taken substantially along line 22 of Fig. 1 and it also discloses portions of a sewing machine feeding and stitching mechanisms.

Fig. 5 represents a diagrammatic illustration of the upper feeding and presser-foot elements which are primarily illustrated in Fig. 4.

The present invention is herein illustrated as applied to a machine of the type disclosed in my U. S. Patent No. 2,292,258; issued August 4, 1942. That portion of the sewing machine shown comprises a bed I upon which is suitably mounted the work-supporting bed-plate 2 fitted with a throat-plate 3. Mounted below the throat-plate 3, is the usual feed-bar 4 having a feed-dog 5 which operates through the throat-plate slots 6 and 'l for the purpose of cooperating with an upper feed-dog 8 in the feeding of the work over the bed-plate 2. Disposed above the throat-plate 3 is a vertically reciprocatory presser-foot 9 and the usual needle I0 which, in the machine illustrated, cooperates with the feed-dogs 5 and 8 in the feeding of the work. Cooperating with the needle H! in the formation of stitches is a looptaker H which is mounted below the throatplate in the usual manner.

Referring more particularly to the present invention, the steel throat-plate 3 is mounted, by means of screws I2, upon a substantially C-shaped steel saddle comprising a cross-member I3 and legs l4 and I5. As may be best seen in Fig. 2, the cross-member I3 is beveled in order to afford proper clearance for the feed-bar 4.

The leg portions l4 and I5 of the saddle underlie the bed-plate edge portions as at [6 in order to afford means whereby the saddle may be secured to the under portions of the bed-plate 2. Bolts I! are provided for securing the saddle to the bed-plate. The upper portion of these bolts are formed with shoulders l8 abutting the lower surface of the bed-plate 2, which latter is provided with apertures for the purpose of receiv- 3 ing the heads of the bolts. These bolt heads are riveted over as at l9 against a spot-faced portion of the bed-plate, thereby to permanently secure the bolts in depending relation therewith.

As may be best seen from Fig. 3, the saddle-legs l4 and [5 are suitably bored to receive the bolts or posts ll, of which the lower ends are threaded as at in order to receive the nuts 2!.

The upper faces of the saddle-legs I 4 and 15 are recessed to receive fiber or rubber washers 22 which are interposed between said legs andthe bed-plate 2 to completely insulate the saddle from the bed-plate. Collars 23 of the same ma terial embrace the bolts within the bores of the legs, thereby effectively to prevent the bolts 11 from engaging the saddle legs.

In order to urge the'throat-plate 3 resiliently towards the presser-foot 9, there are provided coil-springs 24 which are interposed between the nuts 2i and steel washers 25. Placed between each of these steel washers 25 and the shouldered portions of leg-apertures 26 are a pair of fiber or rubber Washers 2? which completely insulate the springs 25 and steel washers 25 from the legs 14 and [5. The tension of the springs 24 may be varied by adjusting the positions of the nuts 2! upon the bolts l'l,

Referring to Fig. 4, the machine illustrated is provided with a needle-feed mechanism as shown in my U. S. Patent No. 2,329,681, September 14, 1943. In the present instance, the needle-bar frame 23 has a bearing lug 29 in which the top feed-bar 30 is slidingly mounted so that the frame 28 will vibrate the feed-bar 30 in the line of feed along with the needle-bar 3d.

The usual type of top-feeding foot 3 is carried by the lower end of the top feed-bar 30 whose upper end is provided with a cross-pin 32 which is slidingly received within the forked free end 33 of a substantially horizontally disposed feedlift crank 3G. The confined end of this crank is pivotally carried as at 35 by the rear portion of the machine head 36.

The machine head 36 is provided with a vertically disposed stationary bearing member 3i carried by a rock-shaft which is journaled in the machine head 36 in parallel relation with the main shaft 46. An eccentric l! carried by the main shaft imparts rocking movements to this rock-shaft 4-5 by means of a connecting pitman rod 48.

Bearing downwardly upon the feed-lift crank 34, at a point between the bell-crank pivot point 45 and the free end thereof, is one end of a spring-depressed lever 49 which extends backwardly along the machine bracket-arm. A steel ball 50 is placed between the spring lever 42 and feed-lift crank 34 in order to prevent the spring lever from exerting any side thrust upon the lat ter element.

The oscillating motions of the above noted rock-shaft 45 cause the bell-crank lever to swing in a vertical plane about its pivot M in the feedlift crank 35, so that the arm 48 of the bellcrank lever tends successively to lift and depress the presser-bar 38. When the presser-bar is depressed, however, its presser-foot 9 engages the work upon the throat-plate 3 and further movement of the bell-crank lever can only result in raising the pivot point 4! thereof, which latter action will, of course, raise the free end 33 of the feed-lift crank 34 with the consequence that the top feed-bar 30 is lifted clear of the work. Continuous oscillations of the rock-shaft will, therefore, cause the presser-bar 38 and the top feed-bar 30 alternately to rise and fall, and the spring-depressed lever 49 being in continuous engagement with the feed-lift crank 34, will have its force transmitted either to the presser-bar or to the top feed-bar, depending upon which one of the two elements is in engagement with the throat-plate or work. The motions of the rockshaft 45 are synchronized with those of the needle-bar 3| so that the usual compound feeding motions will be effected.

From the above, it may be readily understood that the rapidly reciprocating feet 8 and 9, impart successive blows upon the throat-plate 3 which would result in the production of undesirable noises and vibration if the present throatplate was not provided with means whereby the force of the blows could be absorbed.

Thus, as the present throat-plate is supported by the coil-spring means, it is adapted to absorb the hammer blows of the feet 8 and 9. Furthermore, the provision of the non-metallic washers and collars completely insulate the throat-plate from the machine bed to the end that the throatplate cannot transmit any of its vibrations to the machine proper.

As a further means to help dampen the undesirab e vibrations, the throat-plate has pro vided thereon the relatively massive saddle memher which com rises essentially a plurality of vibrat on-ab orbing protuberances I4 and '5. The added mass of this saddle unit is effective to alter, to an advantage. the natural vibration freouency of the throat-plate.

From the foregoing description, considered in connection with the accompanying drawings, the construction, manner of operation and several advantages of this improved throat-plate unit will be clearly and fully understood. It is apparent that such a unit has a wide variety of uses, and it will be understood that the form, construction and arrangement of the elements employed may be varied. Therefore, the privilege is reserved of resorting to all such legitimate changes therein as may be fairly embodied within the spirit and scope of the appended claims.

Having thus set forth the nature of the invention, what I claim herein is:

1. A sewing machine having a frame provided with a bed-plate and an overhanging head, a pair of reciprocatory work-engaging elements adapted alternately to engage the work on one side thereof, a movable work-engaging element disposed on the other side of the work and arranged to oppose one of said pair of work-engaging elements, a throat-plate opposed to the other of said pair of work-engaging elements, and vibration absorbing devices interposed between said throat-plate and frame to insulate said throat-plate from meta-l-to-metal engagement with said frame.

2. A sewing machine having a frame provided with a bed-plate and an overhanging head, a pair of reciprocatory work-engaging elements adapted alternately to engage the work on one side thereof, a movable work-engaging element disposed member to which said throat-plate is secured, 5

said saddle member having a mass greater than that of said throat-plate, and vibration absorbing means interposed between said saddle and said bed-plate.

f FREDERICK F. ZEIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Rogan Aug. 28, 1883 Mueller Nov. 11, 1924 Waterman June 27, 1933 Williams Mar. 30, 1937 Snyder Apr. 26, 1938 Schaelchlin June 17, 1941 

